html,body{
    padding: 0;
    margin: 0;
}
.app{
    width: 800px;
    height: 500px;
    margin: 50px auto;
    background: url(./assect/bg.jpg);
    background-size: cover;
    position: relative;
}
.fff_out{
    position: absolute;
    top:0; 
    width: 600px;
    height: 500px;
    background-color: #fff;
    transition:left 0.5s;
    /* -webkit-transition:left 3s; */
}
.fff_out_left{
    left: 0;
}
.fff_out_right{
    left: 200px;
}
.txt{
    position: absolute;
    top:0;
    width: 100px;
    height: 500px;
    color: #fff;
    transition:color 0.2s;
    transition:width 1s;
}
.widthNone{
    color:rgba(0,0,0,0);
    width: 0;
}
.left_text{
    left: 50px;
}
.right_text{
    right: 50px;
}
.txt .btn{
    position: absolute;
    bottom: 100px;
    left: 0;
    right: 0;
    text-align: center;
    line-height: 26px;
    height: 26px;
    border-radius: 13px;
    border: 2px solid #fff;
}


